Hey Farmgirl, I think at one stage or another and after trying so long to have a baby you do wounder if you should be a mum or not. I think that's only because you haven't seen it in yourself.
For a long time I thought that if I couldn't have a baby on my own it meant it wasn't to be mum.... which is not true.... why give up on what you really want.
You and your DH are planning to have a family and IVF shows that you will do anything to help mother nature along and if your friends make comments other than supportive and encouraging they clearly don't understand how much this means to you.
Take care of yourself and look forward for the day you hold that little bundle